ffmpeg的nvdec解码结果数据格式为 AV_PIX_FMT_CUDA，实际使用中后续接算法需要转为RGB。算法跑在显卡上，解码也在显卡上，所以转换也定为直接在显卡上进行。
关于ffmpeg的nvdec解码的网上博客写的比较多，个人参考的一个比较好的 https://blog.csdn.net/qq_40116098/article/details/120704340
这里只记录解码出来的AV_PIX_FMT_CUDA格式的AVFrame数据转为RGB数据。
基于CUDA的代码实现：
#include "cuda_kernels.h" #include <builtin_types.h> #include "common/inc/helper_cuda_drvapi.h" typedef unsigned char uint8; typedef unsigned int uint32; typedef int int32; #define COLOR_COMPONENT_MASK 0x3FF #define COLOR_COMPONENT_BIT_SIZE 10 namespace cuda_common { #define MUL(x,y) ((x)*(y)) __constant__ float constHueColorSpaceMat2[9]; //默认分配到0卡上，未找到分配到指定卡上设置方法，当前也未用到，先注释 __device__ void YUV2RGB2(uint32 *yuvi, float *red, float *green, float *blue) { float luma, chromaCb, chromaCr; // Prepare for hue adjustment luma = (float)yuvi[0]; chromaCb = (float)((int32)yuvi[1] - 512.0f); chromaCr = (float)((int32)yuvi[2] - 512.0f); // Convert YUV To RGB with hue adjustment *red = MUL(luma, constHueColorSpaceMat2[0]) + MUL(chromaCb, constHueColorSpaceMat2[1]) + MUL(chromaCr, constHueColorSpaceMat2[2]); *green = MUL(luma, constHueColorSpaceMat2[3]) + MUL(chromaCb, constHueColorSpaceMat2[4]) + MUL(chromaCr, constHueColorSpaceMat2[5]); *blue = MUL(luma, constHueColorSpaceMat2[6]) + MUL(chromaCb, constHueColorSpaceMat2[7]) + MUL(chromaCr, constHueColorSpaceMat2[8]); } __device__ unsigned char clip_v(int x, int min_val, int max_val) { if (x>max_val) { return max_val; } else if (x<min_val) { return min_val; } else { return x; } } // CUDA kernel for outputing the final RGB output from NV12; extern "C" __global__ void CUDAToBGR_drvapi(uint32 *dataY, uint32 *dataUV, size_t pitchY, size_t pitchUV, unsigned char *dstImage, int width, int height) { int32 x, y; // Pad borders with duplicate pixels, and we multiply by 2 because we process 2 pixels per thread x = blockIdx.x * (blockDim.x << 1) + (threadIdx.x << 1); y = blockIdx.y * blockDim.y + threadIdx.y; if (x >= width) { return; } if (y >= height) { return; } uint32 yuv101010Pel[2]; uint8 *srcImageU8_Y = (uint8 *)dataY; uint8 *srcImageU8_UV = (uint8 *)dataUV; // Read 2 Luma components at a time, so we don't waste processing since CbCr are decimated this way. // if we move to texture we could read 4 luminance values yuv101010Pel[0] = (srcImageU8_Y[y * pitchY + x]) << 2; yuv101010Pel[1] = (srcImageU8_Y[y * pitchY + x + 1]) << 2; int32 y_chroma = y >> 1; if (y & 1) // odd scanline ? { uint32 chromaCb; uint32 chromaCr; chromaCb = srcImageU8_UV[y_chroma * pitchUV + x]; chromaCr = srcImageU8_UV[y_chroma * pitchUV + x + 1]; if (y_chroma < ((height >> 1) - 1)) // interpolate chroma vertically { chromaCb = (chromaCb + srcImageU8_UV[(y_chroma + 1) * pitchUV + x] + 1) >> 1; chromaCr = (chromaCr + srcImageU8_UV[(y_chroma + 1) * pitchUV + x + 1] + 1) >> 1; } yuv101010Pel[0] |= (chromaCb << (COLOR_COMPONENT_BIT_SIZE + 2)); yuv101010Pel[0] |= (chromaCr << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2)); yuv101010Pel[1] |= (chromaCb << (COLOR_COMPONENT_BIT_SIZE + 2)); yuv101010Pel[1] |= (chromaCr << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2)); } else { yuv101010Pel[0] |= ((uint32)srcImageU8_UV[y_chroma * pitchUV + x] << (COLOR_COMPONENT_BIT_SIZE + 2)); yuv101010Pel[0] |= ((uint32)srcImageU8_UV[y_chroma * pitchUV + x + 1] << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2)); yuv101010Pel[1] |= ((uint32)srcImageU8_UV[y_chroma * pitchUV + x] << (COLOR_COMPONENT_BIT_SIZE + 2)); yuv101010Pel[1] |= ((uint32)srcImageU8_UV[y_chroma * pitchUV + x + 1] << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2)); } // this steps performs the color conversion uint32 yuvi[6]; float red[2], green[2], blue[2]; yuvi[0] = (yuv101010Pel[0] & COLOR_COMPONENT_MASK); yuvi[1] = ((yuv101010Pel[0] >> COLOR_COMPONENT_BIT_SIZE) & COLOR_COMPONENT_MASK); yuvi[2] = ((yuv101010Pel[0] >> (COLOR_COMPONENT_BIT_SIZE << 1)) & COLOR_COMPONENT_MASK); yuvi[3] = (yuv101010Pel[1] & COLOR_COMPONENT_MASK); yuvi[4] = ((yuv101010Pel[1] >> COLOR_COMPONENT_BIT_SIZE) & COLOR_COMPONENT_MASK); yuvi[5] = ((yuv101010Pel[1] >> (COLOR_COMPONENT_BIT_SIZE << 1)) & COLOR_COMPONENT_MASK); // YUV to RGB Transformation conversion YUV2RGB2(&yuvi[0], &red[0], &green[0], &blue[0]); YUV2RGB2(&yuvi[3], &red[1], &green[1], &blue[1]); dstImage[y * width * 3 + x * 3] = clip_v(blue[0] * 0.25,0 ,255); dstImage[y * width * 3 + x * 3 + 3] = clip_v(blue[1] * 0.25,0, 255); dstImage[width * y * 3 + x * 3 + 1] = clip_v(green[0] * 0.25,0 ,255); dstImage[width * y * 3 + x * 3 + 4] = clip_v(green[1] * 0.25,0, 255); dstImage[width * y * 3 + x * 3 + 2] = clip_v(red[0] * 0.25, 0, 255); dstImage[width * y * 3 + x * 3 + 5] = clip_v(red[1] * 0.25,0 ,255); } cudaError_t setColorSpace2(e_ColorSpace CSC, float hue) { float hueSin = sin(hue); float hueCos = cos(hue); float hueCSC[9]; if (CSC == ITU601) { //CCIR 601 hueCSC[0] = 1.1644f; hueCSC[1] = hueSin * 1.5960f; hueCSC[2] = hueCos * 1.5960f; hueCSC[3] = 1.1644f; hueCSC[4] = (hueCos * -0.3918f) - (hueSin * 0.8130f); hueCSC[5] = (hueSin * 0.3918f) - (hueCos * 0.8130f); hueCSC[6] = 1.1644f; hueCSC[7] = hueCos * 2.0172f; hueCSC[8] = hueSin * -2.0172f; } else if (CSC == ITU709) { //CCIR 709 hueCSC[0] = 1.0f; hueCSC[1] = hueSin * 1.57480f; hueCSC[2] = hueCos * 1.57480f; hueCSC[3] = 1.0; hueCSC[4] = (hueCos * -0.18732f) - (hueSin * 0.46812f); hueCSC[5] = (hueSin * 0.18732f) - (hueCos * 0.46812f); hueCSC[6] = 1.0f; hueCSC[7] = hueCos * 1.85560f; hueCSC[8] = hueSin * -1.85560f; } cudaError_t cudaStatus = cudaMemcpyToSymbol(constHueColorSpaceMat2, hueCSC, 9 * sizeof(float), 0, cudaMemcpyHostToDevice); float tmpf[9]; memset(tmpf, 0, 9 * sizeof(float)); cudaMemcpyFromSymbol(tmpf, constHueColorSpaceMat2, 9 * sizeof(float), 0, ::cudaMemcpyDefault); cudaDeviceSynchronize(); if (cudaStatus != cudaSuccess) { fprintf(stderr, "cudaMemcpyToSymbol failed: %s\n", cudaGetErrorString(cudaStatus)); } return cudaStatus; } cudaError_t CUDAToBGR(CUdeviceptr dataY, CUdeviceptr dataUV, size_t pitchY, size_t pitchUV, unsigned char* d_dstRGB, int width, int height) { dim3 block(32, 16, 1); dim3 grid((width + (2 * block.x - 1)) / (2 * block.x), (height + (block.y - 1)) / block.y, 1); CUDAToBGR_drvapi << < grid, block >> >((uint32 *)dataY, (uint32 *)dataUV, pitchY, pitchUV, d_dstRGB, width, height); cudaError_t cudaStatus = cudaGetLastError(); if (cudaStatus != cudaSuccess) { fprintf(stderr, "NV12ToRGB_drvapi launch failed: %s\n", cudaGetErrorString(cudaStatus)); return cudaStatus; } cudaStatus = cudaDeviceSynchronize(); if (cudaStatus != cudaSuccess) { fprintf(stderr, "cudaDeviceSynchronize returned error code %d after launching NV12ToRGB_drvapi !\n", cudaStatus); return cudaStatus; } return cudaStatus; } }
对外接口为 CUDAToBGR 函数，核心实现在 CUDAToBGR_drvapi 函数中。
其中输入参数把Y和UV分开了，其原因是ffmpeg对 AV_PIX_FMT_CUDA 格式数据，在AVFrame中data[0]和data[1]都存在值，AV_PIX_FMT_CUDA 数据其实应该就是显卡上的NV12数据，所以个人推测data[0]是Y数据，data[1]是UV数据。实际转换的效果基本证明这个推测是对的。
调用以实现转换：
先设置颜色空间参数
cuda_common::setColorSpace2( ITU709, 0 );
然后调用以转换：
if (gpuFrame->format == AV_PIX_FMT_CUDA) { cudaError_t cudaStatus; if(pHwRgb == nullptr){ cudaStatus = cudaMalloc((void **)&pHwRgb, 3 * gpuFrame->width * gpuFrame->height * sizeof(unsigned char)); } cudaStatus = cuda_common::CUDAToBGR((CUdeviceptr)gpuFrame->data[0],(CUdeviceptr)gpuFrame->data[1], gpuFrame->linesize[0], gpuFrame->linesize[1], pHwRgb, gpuFrame->width, gpuFrame->height); cudaDeviceSynchronize(); if (cudaStatus != cudaSuccess) { cout << "CUDAToBGR failed !!!" << endl; return; } // saveJpeg("/home/cmhu/FFNvDecoder/a.jpg", pHwRgb, gpuFrame->width, gpuFrame->height); // 验证 CUDAToRGB }
其中 pHwRgb 是unsigned char* ,用cudaMalloc分配的在显卡上的数据。 gpuFrame 是 AVFrame *，是用cuvid硬解出来的帧数据。
转换后的数据保存下来的jpeg图片样例：
可以看到效果良好。
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